Make CUPS USB printing play better with the settings page. This change does several things:

chrome/browser/chromeos/printer_detector/printer_detector.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_CHROMEOS_PRINTER_DETECTOR_PRINTER_DETECTOR_H_
 #define CHROME_BROWSER_CHROMEOS_PRINTER_DETECTOR_PRINTER_DETECTOR_H_
 
 #include <memory>
 #include <string>
+#include <vector>
 
 #include "base/macros.h"
+#include "base/memory/ref_counted.h"

[stevenjb, 2017/04/10 19:49:55]

needed?

[Carlson, 2017/04/10 22:16:41]

Removed

+#include "chromeos/printing/printer_configuration.h"
 #include "components/keyed_service/core/keyed_service.h"
 
 class NotificationUIManager;
 class Profile;
 
 namespace chromeos {
 
 // Observes device::UsbService for addition of USB printers (devices with
 // interface class 7).  What it does with this depends on whether or not
 // CUPS printing support is enabled.
 //
 // If CUPS is disabled, the Legacy implementation should be used.  The legacy
 // implementation shows a notification depending on whether there are printer
 // provider apps that declared support for the USB device installed.  If such
 // app exists, the notification notifies the user the printer is ready.
 // Otherwise the notification offers user to search Chrome Web Store for apps
 // that support the printer. Clicking the notification launches webstore_widget
 // app for the printer.  The notification is shown only for active user's
 // profile.
 //
 // If CUPS is enabled, the Cups implementation should be used.  This
 // implementation to guides the user through setting up a new USB printer in the
 // CUPS backend.
 class PrinterDetector : public KeyedService {
  public:
+  class Observer {
+   public:
+    virtual ~Observer() = default;
+
+    // The set of available printers has changed

[stevenjb, 2017/04/10 19:49:55]

nit: .

[Carlson, 2017/04/10 22:16:41]

Done.

+    virtual void OnAvailableUsbPrintersChanged(
+        const std::vector<Printer>& printers) = 0;
+  };
+
   // Factory function for the Legacy implementation.
   static std::unique_ptr<PrinterDetector> CreateLegacy(Profile* profile);
 
   // Factory function for the CUPS implementation.
   static std::unique_ptr<PrinterDetector> CreateCups(Profile* profile);
   ~PrinterDetector() override {}
 
+  // Observer management.  Note these are only implemented for the cups backend.
+  virtual void AddObserver(Observer* observer) {}
+  virtual void RemoveObserver(Observer* observer) {}
+
+  // Get the current set of detected printers.
+  virtual std::vector<Printer> GetPrinters() { return {}; }
+
  protected:
   PrinterDetector() = default;
 
  private:
   friend class PrinterDetectorAppSearchEnabledTest;
 
   virtual void SetNotificationUIManagerForTesting(
       NotificationUIManager* manager) = 0;
 
   DISALLOW_COPY_AND_ASSIGN(PrinterDetector);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_PRINTER_DETECTOR_PRINTER_DETECTOR_H_